Methods, circuits and systems for obtaining impedance or dielectric measurements of a material, under test

ABSTRACT

Certain disclosed methods include: transmitting an excitation signal into the MUT and transmitting a reference signal to a set of magnitude and phase (M/P) detectors; receiving the response signal; separately comparing a magnitude and phase for each of the excitation signal and the reference signal with corresponding detection ranges for a first one of the M/P detectors; separately comparing a magnitude and phase for each of the response signal and the reference signal with corresponding detection ranges for a second one of the M/P detectors; iteratively adjusting the excitation signal until the response signal has both a magnitude and a phase within the corresponding detection ranges for the second M/P detector; and iteratively adjusting the reference signal until the reference signal has both a magnitude and a phase within the corresponding detection ranges for the first and the second M/P detectors.

PRIORITY CLAIM

This application claims priority to U.S. patent application Ser. No.17/229,958, filed on Apr. 14, 2021, which itself claims priority to U.S.Provisional Patent Application No. 63/010,791, filed on Apr. 16, 2020,the entire contents of each of which is herein incorporated byreference.

TECHNICAL FIELD

The disclosure relates generally to circuits, systems, and methods fordetermining characteristics of a material under test (MUT) by generatingand measuring electric signals at a specific frequency or over a rangeof frequencies to measure the dielectric properties of that MUT. Thedielectric characteristics can then be correlated to a physical propertyor properties of the MUT such as density or moisture.

BACKGROUND

The use of electrical impedance measurements to quantify physicalcharacteristics of construction, manufacturing, and biological materialsis the basis of an increasing number of techniques, including impedancetomography and impedance spectroscopy. An important factor insuccessfully characterizing an MUT is the ability to obtain accurate andrepeatable measurements of electromagnetic properties of an MUT (e.g.,the electrical impedance, admittance, capacitance, permittivity, etc.)of that MUT. These measured values are subsequently converted toinformation about the dielectric properties of the MUT. However,conventional approaches for obtaining electrical data for characterizingMUTs can be both inaccurate and insufficiently repeatable.

SUMMARY

All examples and features mentioned below can be combined in anytechnically possible way.

The present application presents an electronic circuit and measurementsystem for generating electric excitation signals at a specificfrequency or over a range of frequencies that enable accuratemeasurements of response signals after excitation of the MUT. Thetransmitted and response signals can be used to compute the impedanceand dielectric properties of the MUT.

Particular approaches involve generating and measuring electric signalsat a specific frequency or over a range of frequencies to measure theimpedance or the dielectric signature of that MUT. The measurement ofelectrical impedance to quantify physical properties of construction,manufacturing, or biological materials is the basis of a variety ofmeasurement techniques including impedance tomography and impedancespectroscopy. One requirement to successful characterization of an MUTis the accurate and repeatable measurements of the electrical impedance(or admittance) signature, which subsequently is converted toinformation about the dielectric properties of the MUT, which in turncan be correlated with physical (non-electrical) properties of the MUT.Other electromagnetic characteristics can be used to successfullycharacterize an MUT in various implementations. Various particularimplementations include an electronic circuit, measurement system, andmethod for generating electric excitation signals at a specificfrequency or over a range of frequencies that provide accuratemeasurements of the electric signals in response to this excitation ofthe MUT for computation of the impedance and dielectric signalproperties of the MUT.

The subject matter of U.S. Pat. Nos. 5,900,736, 6,414,497, 6,803,771,7,219,024, 9,465,061, and 9,805,146; as well as: US Patent PublicationNo. 2009/0270756, US Patent Publication No. 2012/0130212; US PatentPublication No. 2013/0307564, US Patent Publication No. 2014/0266268, USPatent Publication No. 2014/0278300, US Patent Publication No.2015/0137831, US Patent Publication No. 2015/0212026, US PatentPublication No. 2018/0128934, US Patent Publication No. 2018/0172612;Provisional U.S. Patent Application No. 62/161,9275 (filed on Jan. 25,2018); and Provisional U.S. Patent Application No. 62/661,682 (filed onApr. 24, 2018) describe impedance-related techniques for determiningcharacteristics of materials, and are each incorporated by referenceherein in its entirety.

The methods, electronic circuits and systems of the present subjectmatter relate to the measurement of the impedance as it varies with thedielectric properties of the MUT, as well as electronic devices and/orcomponents for performing such measurements at a specific frequency orover a range of frequencies, with provisions for the characterization ofthe excitation (also referred to as “transmit”), the response (alsoreferred to as “received”), and reference signals to produce a measuredsignal within a desired range of the electronic measuring componentsover the frequency range, based upon the magnitude or strength and phaseshift of the measured signal for the specific frequency or range offrequencies.

In some cases, a method of characterizing a response signal fordetecting physical characteristics of a material under test (MUT)includes: transmitting an excitation signal into the MUT using atransmitting electrode on a sensor array and transmitting a referencesignal to a set of magnitude and phase (M/P) detectors; receiving aresponse signal from the MUT via a receiving electrode on the sensorarray based on the excitation signal; separately comparing a magnitudeand phase for each of the excitation signal and the reference signalwith corresponding detection ranges for a first one of the M/Pdetectors; separately comparing a magnitude and phase for each of theresponse signal and the reference signal with corresponding detectionranges for a second one of the M/P detectors; and iteratively adjustingthe excitation signal until the response signal has both a magnitude anda phase within the corresponding detection ranges for the second M/Pdetector; and iteratively adjusting the reference signal until thereference signal has both a magnitude and a phase within thecorresponding detection ranges for the first and the second M/Pdetectors.

In additional cases, a system is configured to characterize a responsesignal for detecting physical characteristics of a material under test(MUT). In these cases, the system can include: a sensor array forcommunicating with the MUT; a set of magnitude and phase (M/P)detectors; a signal generator coupled with the set of M/P detectors andthe sensor array; and a computing device configured to control processesincluding: initiating: a) transmission of an excitation signal into theMUT with a transmitting electrode on the sensor array and b)transmission of a reference signal to the set of magnitude and phase(M/P) detectors; receiving a response signal from the MUT via areceiving electrode on the sensor array based on the excitation signal;separately comparing a magnitude and phase for each of the excitationsignal and the reference signal with corresponding detection ranges fora first one of the M/P detectors; separately comparing a magnitude andphase for each of the response signal and the reference signal withcorresponding detection ranges for a second one of the M/P detectors;iteratively adjusting the excitation signal until the response signalhas both a magnitude and a phase within the corresponding detectionranges for the second M/P detector; and iteratively adjusting thereference signal until the reference signal has both a magnitude and aphase within the corresponding detection ranges for the first and thesecond M/P detectors.

Particular aspects of the present subject matter provide electroniccircuits, systems, and methods to apply an electronic circuit which: 1)generates an excitation signal and a reference signal at a specificfrequency or over a range of frequencies; 2) applies the excitation asignal to a material under test (MUT) (which may include one or moresubcomponents); 3) characterizes the response signal with respect to thereference signal; 4) determines the magnitude and phase relationshipbetween the response signal produced in presence of the MUT relative tothe reference signal; 5) computes the impedance and dielectricproperties of the MUT (and in some cases, subcomponents); and 6) appliesthe measured dielectric properties to a physical model to correlate themeasurement to a physical property or properties of the MUT (or a sampleof the MUT that has been subjected to engineering testing to determinedesired information about physical properties). The approaches describedherein can include characterization methods for the measuring circuitboard and sensor system, as well as a method to collect information inthe form of electrical quantities with the circuit board and a sensorsystem.

Various embodiments of the disclosure relate generally to an electroniccircuit and system for the measurement of the impedance to electriccurrent through sensing system in communication with a material undertest (MUT) and subsequent extraction of the dielectric properties of theMUT. In some cases, the system includes a circuit having magnitude andphase detectors to measure the change in magnitude or strength and phasedifference between a reference signal and an excitation (or transmit)signal and between the reference signal and the response (or received)signal produced by the transit of the excitation signal through the MUT.The system can include at least one computing device configured tocontrol the generation of the excitation and reference signals, toevaluate the measured signal levels, and to adjust excitation and/orreference signals to produce input signals to the magnitude and phasedetectors and other circuit components that result in best performanceof these detectors and components. Circuits according to variousembodiments can include a signal strength determiner and/or phasedeterminer for determining the phase shift between the excitationsignal, the reference signal, and the response signal specific to theMUT. The strength and phase determiner may be combined in a singlecircuit component. According to various embodiments, the measureddifference in signal strength and phase are used to compute the(complex) electrical impedance and dielectric properties of the MUT.This (MUT/system-specific) impedance or the (MUT-specific) dielectricproperty can be correlated with a physical property or properties of theMUT. The system may be operated at a single frequency, or over a rangeof frequencies.

In some particular embodiments, a system can include: a signal generatorwhich generates the excitation signal and the reference signal; anexcitation electrode connected with the signal generator and inelectrically conductive or non-conductive contact with a material undertest (MUT); a receiving electrode in electrically conductive ornon-conductive contact with the material under test (MUT) which is partof the return path of the excitation current flowing from the excitationelectrode through the MUT to the receiving electrode as the responsesignal; a reference signal which is compared to the excitation signaland the response signal at the receive electrode by a magnitude detectorand/or phase detector; and at least one computing device connected withthe signal generator, the signal strength determiner(s) and/or phasedeterminer(s) for the excitation and reference signals and for theresponse and reference signals, the at least one computing deviceconfigured to: send a control signal to the signal generator to initiateand conduct an excitation signal to the MUT via the excitation electrodeand to the excitation-to-reference strength and phase determiner at aselected frequency or over a range of frequencies.

Implementations may include one of the following features, or anycombination thereof.

In some particular embodiments, the at least one computing devicereceives digitized strength and phase data from analog to digitalconverters connected to the output of the strength and/or phasedeterminer(s) and communicates the data to another computing device tobe used to compute the measured impedance or dielectric property, and tocorrelate impedance or dielectric property with a physical model of theMUT to quantify a physical property or properties of the MUT.

In particular aspects, the computing device is further configured to:compute an electromagnetic property of the MUT based on the measuredmagnitude and phase for the response signal and the reference signal;and correlate the electromagnetic property with a physical property ofthe MUT based on a physical model of the MUT or a laboratory (orengineering) test of the MUT, wherein the electromagnetic propertycomprises one or more of: impedance, susceptance, permittivity oradmittance.

In some particular embodiments, the at least one computing deviceprovides the computation of the measured impedance or the dielectricproperty to be correlated with a physical model of the MUT to quantify aphysical property or properties of the MUT.

In some particular embodiments, the at least one computing deviceprovides the controlling function for the signal generator(s),switch(es), and other controllable elements of the circuit.

In particular aspects, the first M/P detector provide a reading of themagnitude and phase of the excitation signal and the reference signal,and the second M/P detector provides a reading of the magnitude andphase of the reference signal and the response signal.

In certain cases, the readings are obtained by a computing deviceconfigured to control the iterative adjustment (via the signalgenerator) of the amplitude and phase of the excitation signal and thereference signal.

In some implementations, the reading for each of the excitation signal,the reference signal and the response signal comprises separatemagnitude and phase components.

In particular cases, the iteratively adjusting includes adjusting anamplification of the excitation signal and/or the reference signal.

In some aspects, a method further includes, after verifying that theexcitation signal produces a response signal with a magnitude and phasewithin the corresponding detection ranges of the second M/P detector anda reference signal with a magnitude and phase within the correspondingdetection ranges for both the first and the second M/P detectors:analyzing data obtained by the first and second M/P detectors using adata model about physical characteristics of the MUT to detect at leastone physical characteristic of the MUT.

In certain aspects, the analyzing includes correlating impedance ordielectric values for the MUT with an impedance value-to-physicalcharacteristic correspondence table or a dielectric value-to-physicalcharacteristic correspondence table. In some implementations, thecorrespondence table(s) are developed using a physical model of the MUTor by physical sampling or engineering evaluations of the MUT.

In particular implementations, a method further includes converting thereference signal, the excitation signal and the response signal fromanalog format to digital format prior to separately comparing thereference signal, the excitation signal and the response signal with thecorresponding detection ranges for the first and second M/P detectors.

In some cases, the transmitting electrode includes a single transmittingelectrode.

In certain aspects, the receiving electrode includes a single receivingelectrode that surrounds the transmitting electrode.

In particular implementations, the receiving electrode includes aplurality of receiving electrodes, and the method further includesswitching between the plurality of receiving electrodes for the responsesignal using an electrode switch.

In some aspects, the excitation signal and the reference signal are bothgenerated by a signal generator with a common control signal, and theexcitation signal and the reference signal have a common frequency and adistinct magnitude and/or phase.

Particular aspects of the present subject matter provide a system togenerate electric signals at a specific frequency or over a range offrequencies and with varying levels of strength or magnitude to secureimpedance or dielectric measurements on a Material Under Test (MUT)which then can be correlated with physical properties of the MUT. Thesystem may include: at least one computing means which can receiveparameters for a physical model of the MUT (and/or physical/engineeringtesting data about the MUT) and digitize data for the computation of theimpedance or dielectric properties of the MUT; transmit control signalsto the at least one signal generator and circuit components; andtransmit data to a user interface; the at least one signal generatorwhich generates two electric signals at a specific frequency or over arange of frequencies and at various amplitudes and phases of which: anexcitation signal which is transmitted to an electrode in electricallyconducting or non-conducting communication with the MUT and to the firstof the at least two magnitude and phase detectors; and a referencesignal which is transmitted to one of the at least two of the firstmagnitude and phase detector and the second of the at least twomagnitude and phase detectors. The excitation signal which istransmitted to an electrode in communication with the MUT, produces acurrent through the MUT which is collected at least one receivingelectrode which is in electrically conducting or non-conductingcommunication with the MUT and where the current is converted to avoltage (referred to as the received) signal that is transmitted to thesecond of the at least two magnitude and phase detectors. The magnitudeand phase of the excitation signal relative to the reference signal fromone of the at least two magnitude and phase detectors is transmitted asdigital data to the at least one computing means. The magnitude andphase of the received signal relative to the reference signal fromanother of the at least two magnitude and phase detectors is transmittedas digital data to the at least one computing means. The at least onecomputing means processes the digitized magnitude and phase data. The atleast one computing means transmits the processed data to a userinterface which communicates the desired physical properties of the MUT.The material under test may be a soil.

Optionally, the material under test may be any material under test thatproduces a complex impedance spectrum when excited with methods ofElectrical Impedance Spectroscopy (EIS). The specific frequency or rangeof frequencies applied may, in particular, fall within the range of 10kHz to 100 MHz, and in some cases, 100 KHz to 100 MHz. In additionalcases, a method comprises: at least one signal generator generating anelectric excitation signal under control of an at least one computingmeans at a specific frequency or over a range of frequencies at specificamplitude within a range of amplitudes and a fixed phase whose voltagesignal is transmitted to an electrode in communication with a materialunder (MUT) and produces an electric current through the MUT to areceiving electrode which is in electrically conducting ornon-conducting communication with the MUT. The current collected at thereceiving electrode is converted to a voltage signal (received signal)which is transmitted to one of the at least two magnitude and phasedetectors where the at least one computing means determines if theamplitude of the received signal falls within the design amplitude inputrange of the magnitude and phase detector. If the amplitude of thereceived signal is not within the desired range for the magnitude andphase detector and the magnitude of the received signal relative to thereference signal is not within the desired tolerance band of the targetmagnitude, the computing means adjusts the amplitude of the excitationsignal until the measured level is within the desired range andtolerance band. If the amplitude of the received signal is within thedesired input amplitude range for the magnitude and phase detector andthe magnitude of the received signal relative to the reference signal iswithin the tolerance band around the target magnitude, the excitationamplitude is fixed and the at least one computing means then instructsthe at least one signal generator to generate electric signals at afixed frequency or over a range of frequencies at a specific phasewithin a range of phases and at the fixed amplitudes. The electricsignal with varying values of phase is transmitted to an electrode inelectrically conductive or non-conductive communication with the MUT andproduces a current through the MUT which is collected at a receivingelectrode which is in electrically conductive or non-conductivecommunication with the MUT. The current collected at the receivingelectrode is converted to a voltage signal (received signal) which istransmitted to one of the at least two magnitude and phase detectorswhere the at least one computing means determines if the phase of thereceived signal falls within the design input phase range of theamplitude and phase detector. If the phase of the received signal is notwithin the desired range for the magnitude and phase detector is notwithin the desired tolerance band around the desired target phaseoutput, the computing means adjusts the phase of the excitation signaluntil the phase of the received signal is within the desired range andwithin the desired tolerance band. If the phase of the received signalis within the desired phase input range for the level and phase detectorand within the desired tolerance band, the amplitude and phase are fixedand used for the values of the electric excitation signal which ismeasured by the other of the at least two magnitude and phase detectors.The at least one computing means then directs the at least one signalgenerator to generate a reference signal whose amplitude and phase fallwithin the design ranges of the one of the at least two magnitude andphase detectors used to measure the received signal and is adjusted toproduce the magnitude and phase outputs within the desired toleranceband about the target magnitude and phase of the one of the at least twomagnitude and phase detectors used to measure the received signal. Theat least one computing means receives and processes the digitizedmagnitude and phase measurement from the at least two magnitude andphase detectors for the excitation signal and the received signal. Theat least one computing means transmits the processed data to a userinterface which communicates the desired physical properties of the MUT.

Various approaches can be used to determine electromagnetic propertiesof the MUT, including, e.g., one or more of: impedance, susceptance,permittivity or admittance.

Two or more features described in this disclosure, including thosedescribed in this summary section, may be combined to formimplementations not specifically described herein. The system and inparticular its computing device may be configured to carry out themethods described herein. Further variants of the described methodsresult from the intended use of the described system and its components.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features, objectsand advantages will be apparent from the description and drawings, andfrom the claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 . shows an illustration of a phase and magnitude spectrum overthe range of frequencies of interest for a typical soil tested with atypical embodiment of an impedance measurement system.

FIG. 2 Shows and illustration of the Keysight E4990A Impedance Analyzer.

FIG. 3 shows a general configuration of a sensor system including animpedance measurement circuit according to various embodiments of thedisclosure.

FIG. 4 shows an alternate configuration of a sensor system including animpedance measurement circuit with selected circuit elements accordingto various embodiments of the disclosure

FIG. 5 . shows an alternate configuration of a sensor system includingan impedance measurement circuit with selected circuit elementsaccording to various embodiments of the disclosure and an alternatesensor configuration.

FIG. 6 is a flow diagram illustrating processes according to variousimplementations.

FIG. 7 is a flow diagram illustrating processes according to variousadditional implementations.

It is noted that the drawings of the various implementations are notnecessarily to scale. The drawings are intended to depict only typicalaspects of the disclosure, and therefore should not be considered aslimiting the scope of the implementations. In the drawings, likenumbering represents like elements between the drawings.

DETAILED DESCRIPTION

The various circuits, systems, methods, and procedures described hereinare related to the generation of electric signals at a single frequencyor over a range of frequencies for measuring the impedance or dielectricproperties of a material under test (MUT). The frequency or range offrequencies is selected on the basis of the properties of the MUT for animpedance-spectroscopic analysis for the determination of physicalproperties of the MUT. In certain implementations, a single frequency isadequate for tomographic analysis, e.g., as described in US PatentPublication Nos. 2016/0161624, and 2018/0128934, and U.S. Pat. Nos.9,465,061, 9,804,112, and 10,324,052; or for the determination ofphysical properties of selected materials that act as pure capacitors,such as hot mix asphalt, as described in U.S. Pat. Nos. 5,900,736,6,414,497, and 6,803,771. However, for a more complex MUT such as asoil, an impedance-spectroscopic analysis over a range of frequencies isrequired, e.g., as described in U.S. Pat. Nos. 7,219,024, 9,465,061,9,805,146, and 10,161,893. Each of the afore-mentioned applications,publications and issued patents is hereby incorporated by reference inits entirety.

While certain example implementations are described with reference todetermining electromagnetic properties of an MUT such as impedance,various approaches can be used to determine additional, or alternative,electromagnetic properties of the MUT, including, e.g., one or more of:susceptance, permittivity or admittance.

Commonly labeled components in the FIGURES are considered to besubstantially equivalent components for the purposes of illustration,and redundant discussion of those components is omitted for clarity.

While one example MUT described in this disclosure is a soil, thevarious circuits, systems, methods and procedures described herein areapplicable to any material under test that has a complex impedancespectrum, e.g., where Electrical Impedance Spectroscopy (EIS) may beapplied. For example, U.S. Pat. No. 9,465,061 describes a method ofconducting an in-process inspection of solid materials with EIS. Incertain cases, there is a need to conduct in-process inspections andcharacterizations of fluids, as suggested by U.S. Pat. Nos. 9,372,183,9,389,175, and 9,797,855. U.S. Pat. No. 9,389,175 applies an opticaldetection system, and U.S. Pat. Nos. 9,372,183 and 9,797,855 applyimpedance flow cytometry, which counts and characterizes cells. Each ofthe afore-mentioned US patents is incorporated by reference in itsentirety. Additional publications discuss various electromagneticmethods of characterizing dairy products (e.g., milk) and other foodssuch as olive oil, fruits, vegetable oils, cookies, pork, and fish. Inall these examples, the complex impedance spectrum extends over a broadrange of frequencies. This is shown in FIG. 1 , illustratingcorresponding Phase and Magnitude graphs over a frequency range for atypical soil tested with a conventional impedance soil measurementsystem. This broad range of frequencies makes it difficult to secureaccurate measurements that can be used to correlate the measuredimpedance spectrum with a physical property or properties of the MUT,for example, density (or compaction level) and/or moisture level for asoil.

A typical range of frequencies of interest for soils is from about 10kHz to approximately 100 MHz, and in particular cases, from about 100kHz to about 100 MHz. These ranges of frequencies have been shown toprovide an impedance spectrum that can be used to correlate withphysical properties such as density (compaction level) and moisturelevel of the soil. As can be seen in FIG. 1 , the values of the phase(e.g., about 45 degrees up to about 70 degrees) and magnitude (e.g.,about −5 DB to about 5 DB) over the range of frequencies is very large.These values are used to compute the complex impedance of the MUT overthe frequency range of interest. In order to secure accurate data overthe entire range of frequencies, a very sophisticated (and expensive)instrument is typically required. One such instrument is the KeysightTechnologies E4990A Impedance Analyzer, an image of which is shown inFIG. 2 . This Impedance Analyzer is a 30-pound (14 kg) instrument thatis about 17.0-in wide, 9.3-in high and 11.7-in deep (432 mm×239 mm×296mm) and requires laboratory environmental conditions to functioneffectively. As such, the conventional systems and approaches areunwieldy in practical, field use scenarios. To address theseshortcomings in conventional systems and approaches, various disclosedimplementations provide circuits, systems, and methods for use in thefield and/or production environment that are able to secure comparablelevels of data accuracy from an MUT over the desired frequency range.Other approaches to satisfying this objective are presented in US PatentPublication No. 2014/0266268 and U.S. Pat. No. 10,330,616 (eachincorporated by reference in its entirety).

While certain frequency ranges of interest are described herein, otherranges and sub-ranges may also be of interest. For example, the systemsand approaches described herein can be applicable to investigating soilsin frequencies around 32 kHz, e.g., 32 kHz+/−10 kHz, 15 kHz or 20 kHz.

Various commercially available electronic components are described asexamples relating to the various embodiments of the disclosure. Theseare used only for illustrative purposes. Other such components may beused as selected by one skilled in the art.

Referring to FIG. 3 , a schematic depiction of a measurement system (orsimply, system) 100 is shown according to various implementations. Insome cases, the measurement system 100 interacts with (or includes) aplurality of elements (or, sub-systems). In various implementations,system 100 includes a circuit to generate electric signals at a specificfrequency (or over a range of frequencies), along with controls (e.g.,control software such as program code) to communicate with the otherelements of an overall measurement system. As shown in FIGURE (FIG. 3 ,the measurement system 100 is configured to interact with a sensorsystem 200, which in turn communicates with a MUT 210. System 100 isconfigured to receive a physical model 300, which in some example casesis the physical model of the MUT 210, e.g., soil. That is, the physicalmodel 300 can include a physical soil model where the MUT 210 includessoil. Additionally, the sensor system 200 can communicate with aninterface (e.g., user interface) 400, which can be local or remoterelative to the system 100. In some cases, the interface 400 enables auser or other operator to communicate desired physical attributes fortesting of the MUT, e.g., for soil this could include density and/ormoisture.

In various implementations, the sensor system 200 includes a centralexcitation electrode (TX 201) surrounded by a concentric coplanar ringincluding a receiving electrode (RX 202). In some cases, the design ofthe sensor is described in U.S. Pat. Nos. 5,900,736 and 7,219,024. Insome cases, the electrodes 201, 202 are in direct physical contact withthe MUT 210 (e.g., as described with respect to the sensor system inU.S. Pat. No. 5,900,736). In other cases, the electrodes 201, 202 areoffset (separated) from the MUT 210 (e.g., such that a gap or standoffis present between the electrodes 201, 202 and the MUT 210, as isdescribed with respect to the sensor system in in U.S. Pat. No.7,219,024). The sensor system 200 and MUT 210 present a resistive and/orcapacitive load on the circuit of the measurement system 100. The system100 is configured to account for and accommodate for the loadcharacteristics in the sensor system 200 and MUT 210 in order to secureaccurate readings of the change in the magnitude and phase of theresponse signal (received at RX 202) compared to the excitation signal(sent via TX 201).

The physical model of the MUT (e.g., soil) 300 is used in setting theparameters of the circuit in system 100. U.S. Provisional PatentApplication No. 62/661,682 describes a system and method for securing aphysical model of soils for use with system 100.

Certain implementations may replace the physical model and/or supplementthe physical model of the MUT 300 with testing data about physicalcharacteristics of the MUT 300, e.g., an ASTM test determining physicalcharacteristics of the MUT 300.

Interface 400 can include any conventional interface, e.g., a userinterface, to enable a user such as a human user or other communicationsystem to communicate physical properties of the MUT 210 from themeasurement system 100, along with enabling data logging such as dataabout time and/or location of the measurement. Example interfaces caninclude a laptop computer, a tablet, a smart phone, or a dedicated userinterface that is connected (e.g., physically and/or wirelessly) withthe measurement system 100. In any case, the interface 400 is configuredto communicate data from the measurement system 100 in real time, e.g.,in a field-testing environment.

As shown in FIG. 3 , in various implementations, system 100 can includeat least one computing device (e.g., processor and/or memory) 10 that isconfigured to receive data from external systems, e.g., to receive thephysical (MUT) model 300, as well as send and receive data to/from theinterface system 400. In some cases, the physical (MUT) model 300includes information about a desired frequency range and expected valuesof the impedance spectrum for a response from the MUT 210. In certainaspects, information about the desired frequency range needed and thepossible range of measured magnitudes and phases of the impedancespectrum are obtained from prior field testing or laboratory testingwith a system as described in U.S. Provisional Patent Application No.62/661,682. The computing device 10 sends a control signal 11 to asignal generator 12 and receives digital data 18, 19 about on themagnitude (level) and phase of the generated signal from respectivemagnitude and phase (M/P) detectors (e.g., TX and RX) 15 and 17. The(TX) M/P detector 15 compares the excitation TX signal 13 with areference signal 14, both generated by the signal generator 12. The (RX)M/P detector 17 compares the reference signal 14 with the receive(response) RX signal 16 (received at electrode RX 202). The excitationvoltage signal 13 causes current flow from the TX electrode 201 on thesensor, through the MUT 210, to the receiving electrode RX 202, where itis measured as the voltage (response) signal 16 at the RX level andphase detector 17. The (digital) output signals from the magnitude andphase (M/P) detectors 15 and 17 are transmitted to the computing device10. The computing device 10 includes a processor for processing themagnitude and phase data, and a communication system (e.g., conventionalwireless and/or wireless communication system) for sending the resultsas an output, e.g., at interface 400.

FIG. 4 is a schematic depiction of a system 500 according to variousadditional implementations. Commonly labeled features within the FIGUREScan represent the same or similar components, separate descriptions ofwhich may be omitted. In some cases, the system 500 includes at leastone computing device 510, which can include at least one processorand/or a memory. In certain implementations, the computing device 510includes a digital signal controller, e.g., similar to a dsPIC33F 16-bitDigital Signal Controller. However, other microprocessors may be used inadditional implementations. In particular implementations, system 500further includes a signal generator 104, such as a dual channel DirectDigital Synthesis (DDS) chip. The signal generator 104 is connected tothe computing device 510 and is configured to receive controlinstructions as described herein. In particular examples, the signalgenerator 104 includes a device such as an Analog Devices AD9958. Insome cases, multiple single-channel signal generator chips may be usedin place of, or in addition to a dual-channel ship. The signal generator104 is configured to generate two signals at the same frequency atdifferent levels (magnitudes, or strengths): an excitation (TX) signal107, and a reference signal 114. In various implementations, theamplitudes (or, magnitudes) of the signals, as well as the phases, areseparately set at different values for the excitation signal 107 and thereference signal 114. In certain implementations, system 500 includes anamplifier 105 for amplifying the excitation signal 107 and transmittingan amplified (TX) signal 106 to the transmit electrode 201 of the sensorsystem 200 and to a (TX) magnitude and phase (M/P) detector 109. Anexample amplifier 105 can include an AD4870 (from Analog Devices) or asimilar device. In certain implementations, the computing device 501sends an amplifier control signal 103 to control the amplifier 105,e.g., in amplifying excitation signal 107. In the example embodiment ofsystem 500 shown in FIG. 4 , an additional magnitude and phase (M/P)detector 115 is shown for detecting the response signal 121 from theresponse (receiving) electrode 202. In some cases, the M/P detector 115is a similar model/make as M/P detector 109, however, in other cases,these M/P detectors are distinct types. In some cases, the M/P detector115 is an AD8302 or similar device. In practice, the computing device510 instructs the signal generator 104 to generate the reference signal114 and the excitation (TX) signal 107. The reference signal 114 istransmitted to the (TX) M/P detector 109 and also to the response M/Psignal detector (RX) 115. The excitation voltage signal 107, onceamplified and transmitted as TX signal 106, produces current flow fromthe TX electrode 201 on the sensor system 200, through the MUT 210, tothe receiving electrode RX 202. The response signal 121 (in response tothe excitation) is measured at the response M/P detector (RX) 115. Incertain cases, the two M/P detectors 109, 115 (e.g., including anAD8302) produce analog output signals proportional to the logarithmicamplitude ratio (also referred to as magnitude) of and the phasedifference between, respectively, the (TX) excitation signal 106 and thereference signal 114 (in M/P detector 109), and the (RX) receive signal121 and the reference signal 114 (in M/P detector 115). In variousimplementations, these two magnitude and phase analog signals 110, 111,116, 117, one set for each of magnitude and phase detectors (TX 109 andRX 115), are converted to digital signals by an analog to digitalconverter (ADC) 114 prior to being transmitted back to the computingdevice 510 (e.g., for storage, processing, output to a user interface400, etc.). In this example embodiment of system 500, the analog todigital converter (ADC) 114 can include Maxim MAX 1239 analog-to digitalconverter or similar device, that accepts the two sets of analogmagnitude and phase signals and converts them to digital signals fortransmission to the computing device 510.

As noted herein, the amplitude of the excitation signal 107 generatedwith the signal generator 104 may be amplified by the amplifier 105. Insome cases, after passing through the amplifier 105, the TX (voltage)signal 106 is measured with the M/P detector 109 and also applied to theTX (excitation) electrode 201 on the sensor system 200. This TX signal106 causes a current flow through the MUT 210, which is detected at thereceive electrode (RX) 202, where it is transmitted as the measurablevoltage (RX) signal 121 to (RX) M/P detector 115. The amplitude of thereceive (RX) signal 121 is dictated by the amplitude of the (TX) signal106 and the dielectric properties of the MUT 210. By changing theamplitude of the TX signal 106 in either the signal generator 104 or theamplifier 105 (e.g., via instructions from computing device 510), theamplitude of the receive (RX) signal 121 measured by the M/P detector115 is changed. In various implementations, the computing device 510 isconfigured (e.g., programmed) to adjust the amplitude of the output (TX)signal 106 (e.g., via adjustment to the DDS control signal 102 and/orthe amplifier control signal 103) until the receive (RX) signal 121detected at the M/P detector 115 falls within one or more predefinedranges (e.g., an input range for the M/P detector 115, as well as adistinct, but overlapping input range for the M/P detector 109). In somecases, adjusting the receive (RX) signal 121 to fall within one or morerange(s) of the (RX) M/P detector 115 may necessitate a (TX) signal 106that would fall outside the range of the (TX) M/P detector 109. In thesecases, additional measures of proportionate attenuation of the stronger(TX) signal 106 would be required, e.g., by an attenuator before M/Pdetector 109 (not shown). In various implementations, the phase of theexcitation (TX) signal 107 from the signal generator 104 isindependently adjusted by the DDS Control signal 102, in order to adjustthe phase of the receive (RX) signal 121. In other implementations,e.g., where the M/P detector 115 has a broad acceptable phase range(e.g., such as where the M/P detector 115 includes an AD8302 chip), thecomputing device 510 need not independently adjust the phase of theexcitation (TX) signal 107. In particular cases, the amplitude and phaseof the reference signal 114 is specifically defined for TX and RXmeasurements within the input range specified for the M/P detectors(e.g., Analog Devices input specifications for the AD8302 chip).

In various implementations, the ability to independently set theamplitude of the excitation and reference signals to enhance performanceand compatibility of measured signals with the signal input range of themagnitude and phase detectors significantly improves the accuracy ofdata about the MUT 210, as compared with conventional approaches. In theillustration of system 500 (FIG. 4 ), the function of magnitude andphase detection is performed by M/P detectors 109, 115 (e.g., AnalogDevices AD8302 or other comparable magnitude and phase detectors).Having two comparisons against the reference signal (excitation (TX) 106vs. reference 114 and receive (RX) 121 vs. reference 114) enables thecomputing device 510 to compute the complex ratio of excitation (TX)voltage signals and response (RX) voltage signals, expressed in terms ofmagnitude (e.g., logarithmic amplitude ratio) and phase difference as:M _(TX-REF) −M _(RX-REF) =M _(TX-RX)P _(TX-REF) −P _(RX-REF) =P _(TX-RX)

where M_(TX-REF) is the magnitude of the TX signal 107 relative to thereference signal 114;

where M_(RRX-REF) is the magnitude of the RX signal 121 relative to thereference signal 114;

where M_(TX-RX) is the magnitude of the TX signal 107 relative to the RXsignal 121;

where P_(TX-REF) is the phase of the TX signal 107 relative to thereference signal 114;

where P_(RRX-REF) is the phase of the RX signal 121 relative to thereference signal 114; and

where P_(TX-RX) is the phase of the TX signal 107 relative to the RXsignal 121.

After calculating the magnitude and phase differences between theexcitation 107 and response 121 signals, the computing device 510 isconfigured to compare those magnitude and phase differences with thephysical model of the MUT (e.g., soil) 300 to determine physicalproperties of the MUT. As noted herein the physical model of the MUT 300can include magnitude and phase correspondence information (e.g.,tables, correlations, etc.) with physical properties of an MUT. Forexample, for particular MUT types (e.g., soil), the physical model 300includes magnitude and/or phase ranges for signal responses thatcorrespond with particular physical properties or characteristics of theMUT. In particular examples, density or moisture content values orranges are correlated with distinct magnitude and/or phase values orranges, such as those calculated by the computing device 510 using theapproaches described herein.

The measured magnitudes M_(TX-REF) and M_(RX-REF) and phases P_(TX-REF)and P_(RX-REF) can also be used to characterize the measurement systemsdescribed herein (e.g., measurement system 100 in FIG. 3 , measurementsystem 500 in FIG. 4 , and measurement system 600 in FIG. 5 ) whenreplacing an unknown MUT with an object of known electrical properties.For example, in combination with information regarding components of themeasurement systems (from additional independent measurements and/orcomponent specifications), the measurement of materials of knownelectrical properties, such as polyethylene, glass, G9 composite, andgraphite, enables calibration and establishment of a model forconversion of impedance data to dielectric properties.

FIG. 5 shows an additional system 600 according to variousimplementations. System 600 can include a number of components describedwith respect to other systems disclosed herein, e.g., measurementsystems 100 (FIG. 3 ) and 500 (FIG. 4 ). In certain implementations,system 600 includes the measurement system 500 shown and described withreference to FIG. 4 . However, in contrast to the depiction in FIG. 4 ,system 600 includes a distinct sensor system 200A that includes an RXswitch 205 in communication with computing device 510. In certainimplementations, the electrodes in sensor system 200A also differ fromthe electrodes in sensor system 200 (FIG. 4 ). That is, electrodes 201,202, 203 in sensor system 200A are arranged in a linear (orsemi-circular) array of sensors. This arrangement of the sensors permitsan examination of the spatial or tomographic distribution of physicalproperties of the MUT 210. In this example implementation, the sensorsystem 200A includes one excitation electrode (TX) 201 and two distinctreceive (RX) electrodes 202 and 203. A similar electrode arrangement isillustrated in US Patent Publication No. 2018/0128934 and U.S. Pat. Nos.9,465,061 and 9,804,112 (all incorporated by reference herein). Invarious implementations, the excitation electrode (TX) 201 is alwaysactive while one active receive electrode (selected from the receive(RX) electrodes 202 or 203), is selected via a control signal 130 fromthe computing device 510 and the RX switch 205. The volumes of the MUTthat are measured differ between the measurement with transmittingelectrode (TX) 201 and receiving electrode (RX) 202 versus measurementwith transmitting electrode (TX) 201 and receiving electrode (RX) 203.Applying the teachings of U.S. Pat. Nos. 9,465,061 and 9,804,112, theimpedance spectrum of different volumes of the MUT 210 may be determinedand correlated to physical properties of those volumes

In various implementations, the computing devices (e.g., computingdevice 10, FIG. 3 , or computing device 510, FIGS. 4 and 5 ) can beconfigured to adjust the TX signal and RX signal to improve the accuracyof detecting one or more physical characteristics of the MUT 210. Inparticular cases, the computing devices disclosed herein are configuredto match the input excitation signal (e.g., excitation (TX) signal 13 orexcitation (TX) signal 106) and receive signal (e.g., receive (RX)signal 16 or receive (RX) signal 121) to the design range of the M/Pdetectors (e.g., M/P detectors 15, 17 in FIG. 3 and M/P detectors 109,115 in FIGS. 4 and 5 ), as well as adjust the reference signals (e.g.,reference (REF) signal 14 in FIG. 3 and (REF) signal 114 in FIGS. 4 and5 ) to obtain precise and accurate data from the MUT 210 by keeping the(TX) signal 106, the (RX) signal, and the (REF) signal 114 all withinthe input specifications for the (TX) M/P detector 109 and the (RX) M/Pdetector 115.

FIG. 6 is a flow diagram illustrating processes in a method according tovarious implementations. In some cases, the method includescharacterizing an excitation signal, for example, to detect physicalcharacteristics of an MUT. In particular cases, the method also includesdetecting (or characterizing) at least one physical characteristic ofthe MUT using the excitation signal(s). As will be evident, processesdescribed with reference to FIG. 6 can be applied to any of the systemsdisclosed herein, e.g., measurement system 100, measurement system 500and/or measurement system 600. Turning to FIG. 6 , processes caninclude:

Process P1: transmitting an excitation signal (e.g., excitation signal13 or excitation signal 107) into the MUT 210 using a transmittingelectrode (e.g., TX 201) on a sensor array (e.g., sensor system 200,200A) and transmitting a reference signal (e.g., REF 14 or REF 114) to aset of magnitude and phase (M/P) detectors (e.g., M/P detectors 15, 17or M/P detectors 109, 115). In certain cases, as noted herein, theexcitation signal (e.g., excitation signal 13 or excitation signal 107)and the reference signal (e.g., REF 14 or REF 114) are both generated bya signal generator (e.g., signal generator 12 or signal generator 104)with a common control signal (e.g., control 11, control 102), where theexcitation signal and the reference signal have a common frequency and adistinct magnitude and/or phase.

Process P2: receiving a response signal (e.g., receive signal 16 orreceive signal 121) from the MUT 210 via a receiving electrode (e.g., RX202 or RX 203) on the sensor array (e.g., sensor system 200, 200A) basedon the excitation signal (e.g., excitation signal 13 or excitationsignal 107).

Decision D1: separately comparing a magnitude and phase for the responsesignal (e.g., response signal 16 or response signal 121) and thereference signal (e.g., REF 14 or REF 114) with corresponding detectionranges for a second one of the M/P detectors (e.g., M/P detector 17 orM/P detector 115). As described herein, the second M/P detector (e.g.,M/P detector 17 or M/P detector 115) provides a reading (e.g., tocomputing device 10 or 510) of the magnitude and phase of the referencesignal (e.g., REF 14 or REF 114) and the response signal (e.g., responsesignal 16 or response signal 121). The reading for each of the referencesignal (e.g., REF 14 or REF 114) and the response signal (e.g., responsesignal 16 or response signal 121) includes separate magnitude and phasecomponents (e.g., FIGS. 4 and 5 ).

If No to Decision D1, process P3 includes adjusting the excitationsignal (e.g., excitation signal 13 or excitation signal 107), e.g., byincreasing or decreasing the amplitude or magnitude of that signal,e.g., via a control signal 102 to the signal generator (e.g., signalgenerator 13 or signal generator 104). In certain implementations, asillustrated in the embodiments in FIGS. 3 and 4 , the computing device(e.g., computing device 10 or computing device 510) adjusts theamplification of the excitation signal (e.g., excitation signal 107),e.g., generating TX signal 106.

If Yes to Decision D1, Decision D2 includes separately comparing amagnitude and phase for the reference signal (e.g., REF 14 or REF 114)with corresponding detection ranges for each of a first one of the M/Pdetectors (e.g., M/P detector 15 or M/P detector 109) and a second oneof the M/P detectors (e.g., M/P detector 17 or M/P detector 115). Asdescribed herein, the first M/P detector (e.g., M/P detector 15 or M/Pdetector 109) provides a reading (e.g., to computing device 10 or 510)of the magnitude and phase of the excitation signal and the referencesignal, and the second M/P detector (e.g., M/P detector 17 or M/Pdetector 115) provides a reading (e.g., to computing device 10 or 510)of the reference signal and the response signal. In some cases, thereading for each of the received excitation signal, the reference signaland the response signal includes separate magnitude and phase components(e.g., FIGS. 4 and 5 ).

If No to Decision D2 (meaning that reference signal deviates from rangeof both the first and second M/P detectors), proceed to process P4,which includes adjusting the magnitude and/or phase of the referencesignal (e.g., REF 14 or REF 114). As with the decision loop D1, negativeresponses to decision loop D2 can trigger iterative adjustment of thereference signal until both the response signal requirements (DecisionD1) and the reference signal requirements (Decision D2) are satisfied.

A Yes response to Decision D2 means that the response signal (e.g.,receive signal 16 or receive signal 121) and the reference signal (e.g.,REF 14 or REF 114) have both a magnitude and a phase within thecorresponding detection ranges for the second M/P detector (e.g., M/Pdetector 17 or M/P detector 115), and the reference signal (e.g., REF 14or REF 114) has a magnitude and phase with the corresponding detectionranges for both the first and second M/P detectors (e.g., M/P detectors15 and 17 or M/P detectors 109 and 115). In this case, process P5 caninclude analyzing the response signal data from the second M/P detector(e.g., M/P detector 17 or M/P detector 115) and the reference signal(REF 14 or REF 114) using a data model (e.g., physical model 300) aboutphysical characteristics of the MUT 210 to detect at least one physicalcharacteristic of the MUT 210. In particular cases, this analysisincludes correlating impedance or dielectric values in the responsesignal (e.g., receive signal 16 or receive signal 121) with a responsesignal-to-physical characteristic correspondence table (e.g., inphysical model 300).

One or more of the above-noted processes can be modified according tothe various implementations described herein. For example, signals suchas the reference signal, the excitation signal and the response signalcan be converted from analog format to digital format prior toseparately comparing those signals with the corresponding detectionranges for the first and second M/P detectors 109, 115, e.g., asillustrated in FIGS. 4 and 5 . Even further, in cases where the sensorsystem (e.g., sensor system 200A) includes a plurality of distinctreceiving electrodes (e.g., RX 202, RX 203), approaches can includeswitching between receiving electrodes (e.g., RX 202 or RX 203) for theresponse signal using an electrode switch (e.g., RX switch 205, FIG. 5).

FIG. 7 is a flow diagram illustrating processes in an additional methodof detecting a physical characteristic of an MUT 210 using one or moresystems herein. In various implementations, the method is performed byexecution of program code or other programmable instructions at aprocessor such as the processor(s) in the computing device 10 of FIG. 3or the computing device 510 of FIGS. 4 and 5 .

In particular implementations process P101 includes obtaining a physicalmodel of the MUT 300, e.g., as a data file or set of data files, via oneor more communications media. The physical model of the MUT 300 includesthe frequency range over which impedance and/or dielectric data must besecured from the MUT 210 in order to correlate that impedance and/ordielectric data with one or more physical properties of the MUT 210. Themodel 300 can also include information about the amplitudes of theexcitation signal and reference signal for collecting data about the MUT210.

In process P102, the computing device (e.g., computing device 10 orcomputing device 510) transmits a control signal (e.g., control signal11 in FIG. 1 or control signal 102 in FIGS. 4 and 5 ) to a signalgenerator (e.g., signal generator 12 or 104) to initiate generation ofexcitation and reference signals (e.g., signals 13 and 14, or signals107 and 114) at a frequency and amplitude (or over a range offrequencies and amplitudes) within a predefined range(s) of amplitudesand phase for the M/P detectors (e.g., M/P detectors 15, 17 or M/Pdetectors 109, 115). In certain implementations, information about thedesired frequency range and the possible range of measured magnitudesand phases of the impedance spectrum is obtained from prior fieldtesting or laboratory testing with a system as described in U.S.Provisional Patent Application No. 62/661,682, previously incorporatedby reference herein. In the case of measurement system 500 (FIGS. 4 and5 ), the computing device can also be configured to send an amplifiercontrol signal 103 to the amplifier 105 for amplifying the excitationsignal 107.

Also in P102, in response to the control signals from the computingdevice, the signal generator (e.g., signal generator 12 or 104)generates an excitation signal 13 (FIG. 3 ) or 107 (FIGS. 4 and 5 ), andin particular cases, the amplifier 105 (FIGS. 4 and 5 ) amplifies theexcitation signal, according to the commanded frequency, amplitude andphase dictated by the control signals. The TX signal (e.g., TX signal13, FIG. 3 , or TX signal 106, FIGS. 4 and 5 ) is applied to theexcitation electrode 201 in the sensor system 200 (FIGS. 3 and 4 ) or200A (FIG. 5 ). The current produced by the excitation signal passesthrough the MUT 210 and is detected at the receiving electrode 202(FIGS. 3 and 4 ) or multiple receiving electrodes 202, 203 (FIG. 5 ).The detected current at receiving electrode(s) is converted to the(received) voltage signal (e.g., RX signal 16 in FIG. 3 or RX signal 121in FIGS. 4 and 5 ), which is measured in M/P detector(s) (e.g., M/Pdetector 17 in FIG. 3 or M/P detector 115 in FIGS. 4 and 5 ). The M/Pdetector produces magnitude and phase data about the RX signal. In theillustrations in FIGS. 4 and 5 , the magnitude and phase detector isconfigured to produce analog output voltages. In these cases, thevoltages, which are proportional to the measured magnitude and phase,are converted to digital signals in the analog to digital converter 114and transmitted to the computing device 510 101. In FIG. 3 , the M/Pdetector 17 transmits the signals to the computing device 10.

In P103, the amplitude of the receive signal (e.g., receive signal 16 inFIG. 3 or receive signal 121 in FIGS. 4 and 5 ) is compared to thespecified amplitude input range of the M/P detector (e.g., M/P detector17 in FIG. 3 or M/P detector 115 in FIGS. 4 and 5 ). If the measuredmagnitude, which quantifies the amplitude of the receive signal (e.g.,receive signal 16 in FIG. 3 or receive signal 121 in FIGS. 4 and 5 )relative to the commanded amplitude of the reference signal (e.g., REFsignal 14 in FIG. 3 or REF signal 114 in FIGS. 4 and 5 ), indicates thatthe amplitude of the receive signal is not within the specified range,P101 and P102 are repeated with a different amplitude of the excitationsignal (106). In P104, the excitation amplitude is adjusted to bring theamplitude of the receive signal (e.g., receive signal 16 in FIG. 3 orreceive signal 121 in FIGS. 4 and 5 ) within the specified input rangeof the M/P detector (e.g., M/P detector 17 in FIG. 3 or M/P detector 115in FIGS. 4 and 5 ), for example, to produce a desired quality of themagnitude output signal. In some cases, this includes keeping themeasured magnitude of the (TX) signal 106, the (RX) signal, and the(REF) signal 114 all within the input specifications for the (TX) M/P109 and (RX) M/P 115. Otherwise, the procedure moves to process P105 ifthe measured phase of the (TX) signal 106 or the (RX) signal are outsideof the specified phase range limitations for the M/P detector 115, or toprocess P107 if phase adjustments are not necessary.

In P107, the computing device (e.g., computing device 10 or computingdevice 510) adjusts the phase of the signal generated by the signalgenerator (e.g., signal generator 12 or 104) to match the phase of thesignal required for the specified range of the M/P detector (e.g., M/Pdetector 17, FIG. 3 or M/P detector 115, FIGS. 4 and 5 ). The data fromthe last reading from process P105 provides the initial value of phasefor process P106.

In P106, the measured receive signal (e.g., RX signal 16, FIG. 3 , or RXsignal 121, FIGS. 4 and 5 ) is compared to the specified input phaserange for the magnitude and phase detector (e.g., M/P detector 17, FIG.3 or M/P detector 115, FIGS. 4 and 5 ). If the measured phase is notwith in the specified input range of the RX M/P 115 or the TX M/P 109,P106 is repeated with a different phase of the excitation signal (e.g.,TX signal 13, FIG. 3 or TX signal 106, FIGS. 4 and 5 ) with themagnitude of the excitation signal fixed. In P108, the phase is adjustedto bring the phase of the receive signal (e.g., RX signal 16, FIG. 3 ,or RX signal 121, FIGS. 4 and 5 ) within the specified input range ofthe phase detector (e.g., M/P detector 17, FIG. 3 or M/P detector 115,FIGS. 4 and 5 ). Otherwise, the process moves to Process P109.

At this point, the frequency, amplitude and phase of the excitationsignal (e.g., TX signal 13, FIG. 3 or TX signal 106, FIGS. 4 and 5 ) andreceive signal (e.g., RX signal 16, FIG. 3 , or RX signal 121, FIGS. 4and 5 ) are fixed. In P109, the reference signal (e.g., REF 14, FIG. 3or REF 114, FIGS. 4 and 5 ) is adjusted for the receive (RX) magnitudeand phase measurement. The amplitude and phase of this signal isselected to be within the respective specified input ranges of themagnitude and phase detector 115 (e.g. the specifications of the AnalogDevices AD8302) such that the amplitude of the reference signal is asclose as possible to the amplitude of the receive (RX) signal and thephase difference is 90°, where the phase difference can be detected withhighest precision.

In P110, the measured magnitude and phase of the receive signal (e.g.,RX signal 16, FIG. 3 , or RX signal 121, FIGS. 4 and 5 ) are compared totarget output magnitude and phase of the level and phase detector (e.g.,M/P detector 17, FIG. 3 or M/P detector 115, FIGS. 4 and 5 ). If themeasured magnitude and phase from detector (e.g., M/P detector 17, FIG.3 or M/P detector 115, FIGS. 4 and 5 ) is not within specified tolerancebands based on the signal to noise ratios around the target magnitudeand phase, P109 is repeated with a magnitude and phase of the referencesignal (e.g., REF 14, FIG. 3 or REF 114, FIGS. 4 and 5 ) that isincreased or decreased to match the target values. Otherwise, theprocedure is continued in P110.

In P110, the reference signal (e.g., REF 14, FIG. 3 or REF 114, FIGS. 4and 5 ) is adjusted for the excitation (TX) magnitude and phasemeasurement. The amplitude and phase of this signal is selected to bewithin the respective specified input ranges of the magnitude and phasedetector (e.g., M/P detector 15, FIG. 3 or M/P detector 109, FIGS. 4 and5 ) such that the amplitude of the reference signal is approximatelyequal to the amplitude of the TX signal and the phase difference is 90°,where the phase difference can be detected with sufficient precision.

In P112, the measured magnitude and phase of the excitation signal(e.g., TX signal 13, FIG. 3 or TX signal 106, FIGS. 4 and 5 ) arecompared to target output magnitude and phase of the level and phasedetector (e.g., M/P detector 15, FIG. 3 or M/P detector 109, FIGS. 4 and5 ). If the measured magnitude and phase from detector 109 is not withinspecified tolerance bands based on the signal to noise ratios around thetarget magnitude and phase, P111 is repeated with different amplitudeand phase of the reference signal (114). Otherwise, the procedure isrepeated with a different frequency within the specified range offrequencies starting in Process P102 or completed in Process P112.

The computation of the magnitude and phase of the excitation signal 106relative to the receive signal 121 is described herein. These values areused to compute the measured impedance or dielectric properties over therange of frequencies to correlate with the physical properties ofinterest for the MUT.

The functionality described herein, or portions thereof, and its variousmodifications (hereinafter “the functions”) can be implemented, at leastin part, via a computer program product, e.g., a computer programtangibly embodied in an information carrier, such as one or morenon-transitory machine-readable media, for execution by, or to controlthe operation of, one or more data processing apparatus, e.g., aprogrammable processor, a computer, multiple computers, and/orprogrammable logic components.

A computer program can be written in any form of programming language,including compiled or interpreted languages, and it can be deployed inany form, including as a stand-alone program or as a module, component,subroutine, or other unit suitable for use in a computing environment. Acomputer program can be deployed to be executed on one computer or onmultiple computers at one site or distributed across multiple sites andinterconnected by a network.

Actions associated with implementing all or part of the functions can beperformed by one or more programmable processors executing one or morecomputer programs to perform the functions of the calibration process.All or part of the functions can be implemented as, special purposelogic circuitry, e.g., an FPGA and/or an ASIC (application-specificintegrated circuit). Processors suitable for the execution of a computerprogram include, by way of example, both general and special purposemicroprocessors, and any one or more processors of any kind of digitalcomputer. Generally, a processor will receive instructions and data froma read-only memory or a random access memory or both. Components of acomputer include a processor for executing instructions and one or morememory devices for storing instructions and data.

In various embodiments, components described as being “coupled” to oneanother can be joined along one or more interfaces. In some embodiments,these interfaces can include junctions between distinct components, andin other cases, these interfaces can include a solidly and/or integrallyformed interconnection. That is, in some cases, components that are“coupled” to one another can be simultaneously formed to define a singlecontinuous member. However, in other embodiments, these coupledcomponents can be formed as separate members and be subsequently joinedthrough known processes (e.g., fastening, ultrasonic welding, bonding).

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a”, “an” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on”, “engaged to”,“connected to” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto”, “directly connected to” or “directly coupled to” another element orlayer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”,“lower”, “above”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

We claim:
 1. A method of characterizing a response signal for detectingphysical characteristics of a material under test (MUT), the methodcomprising: transmitting an excitation signal into the MUT andtransmitting a reference signal to a set of magnitude and phase (M/P)detectors; receiving the response signal from the MUT based on theexcitation signal; separately comparing a magnitude and phase for eachof the excitation signal and the reference signal with correspondingdetection ranges for a first one of the M/P detectors; separatelycomparing a magnitude and phase for each of the response signal and thereference signal with corresponding detection ranges for a second one ofthe M/P detectors; iteratively adjusting the excitation signal until theresponse signal has both a magnitude and phase within the correspondingdetection ranges for the second M/P detector; and iteratively adjustingthe reference signal until the reference signal has both a magnitude anda phase within the corresponding detection ranges for both the first andsecond M/P detectors.
 2. The method of claim 1, wherein the excitationsignal and the reference signal are both generated by a signal generatorwith a common control signal, and wherein the excitation signal and thereference signal have a common frequency and a distinct magnitude and/orphase.
 3. The method of claim 1, further comprising attenuating theexcitation signal prior to the separately comparing the excitationsignal and the reference signal with the corresponding detection rangesfor the first one of the M/P detectors and the separate comparing of theresponse signal and the reference signal with the correspondingdetection ranges for the second one of the M/P detectors.
 4. The methodof claim 1, wherein the first M/P detector provides a reading of themagnitude and phase of the excitation signal and the reference signal,and wherein the second M/P detector provides a reading of the magnitudeand phase of the reference signal and the response signal.
 5. The methodof claim 4, wherein: the readings are obtained by a computing deviceconfigured to control the iterative adjustment of the excitation signaland the reference signal, and/or the reading for each of the excitationsignal, the reference signal and the response signal comprises separatemagnitude and phase components.
 6. The method of claim 1, furthercomprising down-converting a portion of the excitation signal to apredetermined frequency.
 7. The method 6, wherein the reference signalremains at a fixed frequency while the portion of the excitation signalis down-converted, wherein the predetermined frequency of thedown-converted portion of the excitation signal includes a range ofapproximately 10 kHz to approximately 1 MHz.
 8. The method of claim 7,wherein the reference signal is maintained at a fixed frequency to matcha frequency of a mixer output.
 9. A system configured to characterize aresponse signal for detecting physical characteristics of a materialunder test (MUT), the system comprising: a sensor array forcommunicating with the MUT; a set of magnitude and phase (M/P)detectors; a signal generator coupled with the set of M/P detectors andthe sensor array; and a computing device configured to control processesincluding: initiating: a) transmission of an excitation signal into theMUT with a transmitting electrode on the sensor array and b)transmission of a reference signal to the set of magnitude and phase(M/P) detectors; receiving a response signal from the MUT via areceiving electrode on the sensor array based on the excitation signal;separately comparing a magnitude and phase for each of the excitationsignal and the reference signal with corresponding detection ranges fora first one of the M/P detectors; separately comparing a magnitude andphase for each of the response signal and the reference signal withcorresponding detection ranges for a second one of the M/P detectors;iteratively adjusting the excitation signal until the response signalhas both a magnitude and a phase within the corresponding detectionranges for the second M/P detector; and iteratively adjusting thereference signal until the reference signal has both a magnitude and aphase within the corresponding detection ranges for the first and thesecond M/P detectors.
 10. The system of claim 9, wherein the computingdevice is further configured to: compute an electromagnetic property ofthe MUT based on the measured magnitude and phase for the responsesignal and the reference signal; and correlate the electromagneticproperty with a physical property of the MUT based on a physical modelof the MUT or a laboratory test of the MUT.
 11. The system of claim 9,wherein the excitation signal and the reference signal are bothgenerated by the signal generator with a common control signal, andwherein the excitation signal and the reference signal have a commonfrequency and a distinct magnitude and/or phase.
 12. The system of claim9, wherein the signal generator includes multi-channel signal generationwith three or more channels.
 13. The system of claim 9, wherein thecomputing device is further configured to attenuate the excitationsignal prior to the separate comparing of the excitation signal and thereference signal with the corresponding detection ranges for the firstone of the M/P detectors and the separate comparing of the responsesignal and the reference signal with the corresponding detection rangesfor the second one of the M/P detectors.
 14. The system of claim 9,wherein the first M/P detector provide a reading of the magnitude andphase of the excitation signal and the reference signal, and wherein thesecond M/P detector provides a reading of the magnitude and phase of thereference signal and the response signal.
 15. The system of claim 14,wherein: the readings are obtained by the computing device configured tocontrol the iterative adjustment of the excitation signal and thereference signal, and/or the reading for each of the excitation signal,the reference signal and the response signal comprises separatemagnitude and phase components.
 16. An electronic circuit configured to:generate an excitation signal and a reference signal at a specificfrequency or over a range of frequencies; apply the excitation signal toa material under test (MUT); receive a response signal from the MUT;determine a magnitude and phase relationship between the response signalproduced in presence of the MUT relative to the reference signal;compute impedance and dielectric properties of the MUT based on themagnitude and phase relationship between the response signal and thereference signal; and apply the computed dielectric properties to aphysical model to correlate the measurement to at least one physicalproperty of the MUT.
 17. The electronic circuit of claim 16, wherein anamplitude of the excitation signal and an amplitude of the referencesignal are independently set to control determination of the magnitudeand phase relationship between the response signal and the referencesignal.
 18. The electronic circuit of claim 16, wherein computing theimpedance and dielectric properties of the MUT is performed using acomputational model of the physical characteristics of the MUT and asensing system.
 19. The electronic circuit of claim 16, furtherconfigured to: send a first portion of the excitation signal to amagnitude and phase (M/P) detector and send a second portion of theexcitation signal to a transmitting electrode for application to theMUT; and attenuate the first portion of the excitation signal to producean intermediate signal.
 20. The electronic circuit of claim 19, whereina frequency of the excitation signal varies across a range offrequencies, and wherein a frequency of the intermediate signal varieswith the excitation signal at a lesser amplitude.